Process for centrifugal distribution of liquid physiological specimens

ABSTRACT

This invention discloses an improved process of distributing liquid physiological specimens over a surface, i.e. the filming process in a laboratory, during which a liquid sample is distributed over a specimen-display surface like a conventional laboratory slide. The invention relates to the utilisation of the centrifugal force in a rotating device. By placing the surface that is to be filmed by the sample, in such a way that it is pointed towards the axis of rotation, the influence of the centrifugal force will distribute the sample over the whole surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of and incorporates byreference essential subject matter disclosed in InternationalApplication No. PCT/DK03/00209 filed on Mar. 27, 2003 and Danish PatentApplication No. PA 2002 00514 filed on Apr. 9, 2002.

FIELD OF THE INVENTION

This invention relates to a process for centrifugal distribution ofliquid physiological specimens over a surface with an array of assays,the array being placed in a rotating device and the liquid physiologicalspecimens being distributed on the surface by the dynamic forces of therotation, the surface pointing towards the axis of rotation, the liquidphysiological specimens being forced towards the surface under theinfluence of the dynamic forces of the rotation.

BACKGROUND OF THE INVENTION

Centrifugal distribution of liquids physiological specimens over asurface with an array of assays is often referred to as “filming” bythose working in medical laboratories, and the liquid physiologicalspecimens are often called “samples”.

In this connection, the term “a liquid physiological specimen” is to beunderstood in a very broad manner, covering, of course, physiologicalspecimens like blood and spittle, but also pre-treated DNA extracts arecomprised by the term.

As an example, applying a drop of blood to a slide, where the surface ofthe slide contains an array of assays, takes place in a DNA-testingprocess. When the drop of blood is distributed over the surface of theslide, the elements in the blood will react or connect to the assayswhere they fit, and analysing the slide afterwards will give the resultof the DNA-testing.

To achieve the contact between the elements of the sample and theassays, the elements have to diffuse from the sample to the assays, andobviously the duration of this diffusion will increase with thethickness of the sample layer on the surface of the slide. This willreduce the duration of the process, if the thickness of the layer isreduced, and therefore reducing the thickness of the layer is desirable.

When filming, the main problem to solve is to equally distribute andre-circulate the sample over the whole of the surface, the sample beingdistributed to all the assays in the array. One way of solving thisproblem is to place the array of assays flat in a rotating device, thesurface being in the same plane as the rotational movement. This willforce, or rather throw, the sample along the surface, due to the dynamicreaction to the rotation. In the following, this dynamic reaction willbe referred to as the centrifugal force, and must be understood as theact of a particle moving away from the centre of a rotating movement.

When distributing a sample by throwing it across the surface of thearray of assays, the sample applied to the surface does not distributeequally over the whole surface, reproduction of the result being hard toobtain. A single drop of the sample is not likely to distribute over thewhole surface, and therefore does not necessarily reach all assays inthe array. Therefore, a number of extra drops is applied to the surface,which will increase the duration of each test and the used amount of thesample, which is often expensive. Also, each specimen in the sample willbe forced along the surface, contact between the specimens and all theassays in the array being hard to obtain, which also influences thereproduction ability of the test.

Another known method of overcoming the problems of the filming processis to force the sample through micro channels, in which the array ofassays is contained. This method will reduce the duration of theprocess, but is very sensitive to pollution, the size of the elements inthe sample, and the production of the micro channels.

It is an object of this invention to overcome the difficulties ofreproducing test results. It is a further object of this invention toreduce the duration of each test, and to reduce the used amount of thesample for each test. Yet another object of the invention is to reducethe sensitivity with regard to pollution and to the size of the elementsin the sample.

SUMMARY OF THE INVENTION

The object of this invention is achieved in that the liquidphysiological specimens are applied as drops to an area of the surfaceopposite a drain end, and in that the distribution of the liquidphysiological specimens is controlled by adjusting the position of thesurface relative to the axis of rotating, in such a way that a thin filmof the liquid physiological specimens will be formed over the wholesurface before drops are forced over the edge in the drain end of thesurface. Hereby it is achieved that the elements in the sample areforced in the direction of the assays, and a drop of the sample will becompletely filmed by the dynamic forces. Further, it is achieved thatall assays in the array are in contact with the sample, and that theelements in the sample will have equal and best conditions for diffusionto the assays. Yet further, it is achieved that it is possible tocontrol the direction of the distribution, and the rate at which thesample distributes over the surface.

It is an advantage that the array of assays itself further rotatesaround another axis than that of the rotating device, meaning that theelements in the sample will be distributed to all, or nearly all, assaysin the array.

It is particularly preferred that the surface, to which the sample isapplied, is formed as a hollow in a material part, where the hollowforms a closed container when the material part is covered with a lid,and where the sample is applied to the surface before the lid covers thehollow. The sample is contained in a closed container, and can bere-circulated over the surface without having any disturbing and/ordamaging contact with the surroundings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in detail withreferences to the drawings, showing:

FIGS. 1A-G illustrate a slide having a number of assays, and show theprogression of a liquid sample under centrifugal force.

FIG. 2 is a partly in section perspective view of the rotating device ofthe present invention.

FIG. 3 is a partly in section perspective view of a portion of therotating device of FIG. 2.

FIG. 4 shows an embodiment of an array of assays, placed in a hollow.

FIG. 5 is a perspective view of a device containing two arrays ofassays, placed in a hollow.

FIG. 6 schematically illustrates a rotating array of assays inaccordance with the invention.

FIGS. 7A-E are functional views showing the process or re-circulation inaccordance with FIG. 6.

FIG. 8 schematically illustrates a embodiment of a rotating device.

FIG. 9 schematically illustrates a embodiment of a rotating device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1A shows a sectional view of a slide 1, having a surface 2 with anarray of assays 3. Such slides are widely used in laboratories, e.g. formicroscopic analyses of blood specimens. The slide of FIG. 1A has aframe part 4 along three of the sides, which will be understood from thesectional view in FIG. 1B. The fourth side 5 is formed and works as adrain part, where the specimens can flow away from the surface 2.

The slide 1 is placed in a rotating device 9 of FIG. 2, said devicecomprising several sections 13. FIG. 3 shows one of the sections 13 in asectional view, and with the slide 1 placed in the holder 14. As therotating device is rotating, centrifugal forces will act from the centreof rotation, and at right angle, towards the circumference 12 of therotating device 9. The plunger part 11 of FIG. 2 will be forced towardsthe part 16 of FIG. 3, due to the dynamic forces, and under thispressure liquid sample contained behind part 16 will be dosed as dropsby a capillary part 17, and led through the pipe 18 to the slide 1. Themouth of the pipe ends at the end of the slide where the holder isplaced, and at a certain distance from the slide. The slide itself isplaced in an upright position along the circumference 12 of the rotatingdevice 9, the centrifugal force acting substantially parallel to anormal axis of the surface of the slide. The surface of the slide 1 istherefore substantially parallel to the rotating axis of the rotatingdevice.

The drop 6 in FIGS. 1A and 1B is a drop, which has just left the pipe18, and as the drop hits the surface of the slide, it will bedistributed over the surface by the centrifugal force. This is indicatedby arrows in FIGS. 1C to 1F, and the frame 4 on the three sides of theslide 1 will force the distribution towards the drain part 5 of theslide 1, from where drops 7 will be thrown of the slide. The centrifugalforce has now distributed a thin layer of the sample over the wholesurface, and every assay 3 in the array has got in contact with thesample.

The velocity with which the sample is distributed towards the drain part5 can be controlled by controlling the angular position of the slide,and by controlling the rotational speed of the rotating device. As thedistribution over the surface is controllable, only a very small amountof sample liquid is needed for each slide. As a consequence of thedynamic forces, surface tensions will only have limited effect.

In some test application it is important that the used amount of sampleliquid is reduced to a minimum, and that the applied sample liquid ismaintained on the surface of the slide, and not thrown away over a drainpart as previously described. This is known as re-circulation of thesample along the surface. FIG. 4 shows a structure 19, placed in ahollow, which has a surface 2 with an array of assays 3, and is suppliedwith small pockets 20 placed along the circumference of the structure.This structure is formed as a hollow 19 in a material part 21, shown inFIG. 5, with a lid 22 on top of it. When the lid is placed on top of thematerial part 21, each of the two hollows 19 and 19 a forms a small testvolume, and the assembled material part with lid forms a slide 26.

FIG. 6 shows the slide 26 placed in a rotating device with an axis ofrotation 10, the rotation direction being indicated by an arrow 24. Theslide 26 is placed at a centre line 23 that is placed at an angle Yrelative to the rotating axis 10, and at a distance X from the rotatingaxis 10, the centrifugal force acting on the surface as previouslydescribed with a normal portion. In addition, the dynamic forces willact upon the surface with a tangential portion, the sample being forcedacross the surface. The slide 26 is rotated around the centre line 23,indicated by the arrow 25. The effect of this additional rotation 25will be described with reference to FIG. 7.

FIG. 7A shows a drop of a liquid sample applied to the test volume inthe container, and the lid is then placed on top of the container.Subsequently, the slide 26 is placed in the rotating device, thecentrifugal force acting upon the surface and filming the sample on thearray of assays. Some of the sample will be distributed into the smallpockets, and as the slide 26 rotates around an axis, the liquid samplewill flow from one pocket to the array of assays, and along thecircumference to the next pockets, indicated in FIG. 7B. The shape ofthe pockets will, however, distribute liquid sample over the whole arrayof assays, as the slide 26 is rotated, indicated in FIGS. 7C to 7E. Eachpocket then acts as a collecting area, from where liquid sample onceagain is distributed to the array of assays, and re-circulation occurs.

Re-circulation as described in FIG. 7 has basically the effect knownfrom a washing machine. The sample is again and again washed across thearray of assays, whereby reproduction of the testing is obtained.

FIG. 8 shows another embodiment of a rotating slide in a rotatingdevice. The slide 28 is now formed as a cylinder part, which rotatesaround its own axis 27. The axis 27 is more or less parallel to therotation axis 10 of the rotating device, and the centrifugal force willthus act upon the surface of the slide 28. The array of assays is placedon the inner surface of the slide 28, and on the top and on the bottomthe slide has a frame part 4, extending from the inner surface of thecylinder towards the axis of rotation 27. As a drop of the liquid sampleis applied inside the slide 28, it will be distributed as a column alongthe inner surface, and the column will be placed where the distance fromthe axis of rotation 10 is largest. As the slide is rotated around theaxis 27, the column will wash the whole of the inner surface, and herebyre-circulation will occur.

FIG. 9 shows a third embodiment of a rotating slide in a rotatingdevice. Here the slide is formed as a cone part 30, which rotates aroundits own axis 29. The axis 29 is placed at an angle relative to therotation axis 10 of the rotating device, a part of the inner surface ofthe cone shaped slide being more or less parallel to the rotation axis10 of the rotating device, and the centrifugal force will thus act uponthis part of the inner surface of the cone shaped slide 30. Due to thecentrifugal force, a column of liquid sample 31 will be formed on theinner part of the cone shaped slide, which is more or less parallel tothe axis of rotation 10. As the cone shaped slide is rotated around itsown axis 29, liquid sample will wash the whole inner surface, and herebyre-circulation will occur.

As mentioned in the beginning of the application, the invention can beutilised in laboratories for DNA-testing. However, this application doesnot in any way limit the invention. A slide can contain similar assaysfor reaction with specific elements or different assays for reactionwith a group of elements. The invented process can be utilised fordistribution of a sample over any surface of a slide, and theapplication will then depend on the slide used in the process.

Thus, a portable apparatus for testing purposes on location is apossibility. This could be an apparatus testing for diseases whenconsulting a doctor, or an apparatus testing for cultures of bacteria inwatercourses. Only the slide used in the process defines the applicationfor a given apparatus.

1-4. (canceled)
 5. A process for centrifugal distribution of liquidphysiological specimens over a surface with an array of assays, saidprocess comprising the steps of: placing said array in a rotatingdevice, distributing said liquid physiological specimens to said surfaceby the dynamic forces of the rotation, said surface being pointedtowards the axis of rotation, forcing the liquid physiological specimenstoward said surface under the influence of the dynamic forces of therotation, said liquid physiological specimens being applied as drops toan area of said surface opposite a drain end, the distribution of saidliquid physiological specimens being controlled by adjusting theposition of said surface relative to said axis of rotating, in such away that a thin film of said liquid physiological specimens will beformed over the whole of said surface before drops are forced over theedge in the drain end of the surface.
 6. A process for centrifugaldistribution of liquid physiological specimens over a surface with anarray of assays, said process comprising the steps of: placing saidarray in a rotating device, distributing said liquid physiologicalspecimens to said surface by the dynamic forces of the rotation, saidsurface being pointed towards the axis of rotation, the liquidphysiological specimens being forced towards said surface under theinfluence of the dynamic forces of the rotation, wherein thedistribution of said liquid physiological specimens is controlled byvarying the position or orientation of said surface relative to saidaxis of rotation, in such a way that a thin film of said liquidphysiological specimens is formed on at least varying parts of saidsurface, and in such a way that said thin film is re-circulated acrosssaid array of assays.
 7. A process in accordance with claim 6, whereinsaid control of said surface is caused by a rotating movement around anaxis other than that of the rotating device.
 8. A process in accordancewith claim 6, wherein said surface, to which said liquid physiologicalspecimens are applied, is formed as a hollow in a material part, saidhollow forming a closed container when the material part is covered witha lid, and said liquid physiological specimens being applied to saidsurface before said lid covers said hollow.